The so-called 'technical interview', might include a few questions to test the applicant's ATC and aviation knowledge, but that's not what it's there for.
It's there to determine your suitability to become a trainee ATCO. To determine if you have the right skills. Therefore to pass the interview you don't have to 'know' anything. ATC knowledge is one of many areas we test during the interview.
However, I'd certainly suggest one learns as much as possible before interview. For all the obvious reasons.